Thermal relay



Aug 2, 1932' c. HODGKINS 'RMAL RELAY Filed Sept. 29, 1951 WITNESSES; I INVENTOR G Char/esHHodgkins.

l BY

5) 02M ATTORNEY Patented Aug. 2, 1932 UNITED STATES PATENT OFFICE GHARLES H. nonoxms, or mamas, rnnnsnvama, assrenon 'ro wnsrmo- VANIA THERMAL RELAY 7 Application filed September 29, 1981. Serial No. 565,744.

My invention relates to relays and particularl to thermally actuable'relays.

An ject of my invention is to PIOVldG a relatively simple and highly eflicient means in a thermal rela for varying the value of the current at WlllCh the relay will 0 crate.

My invention is particularly applicable to an electromagnetic thermal relay embodying a current-traversed initially-magnetic member which becomes non-magnetic at a higher temperature, and, in practiclng my invention, I provide an energizing coil and a strip or bar of a suitable magnetlcally-reversible metal, which strip or bar is normally operatively en gaged by a portion of a pivotally-mounted armature structure,-one portion of the armature structure being adjustable relatively to the strip or bar.

In the single sheet of drawing:

Figure 1 is a view'partly in section and mainly in side elevation, of a thermal relay embodying my invention;

Fig. 2 is a top plan view of the device shown in Fig. 1, and

Fig. 3 is a view,'in front elevation, of the device shown in Fig. 2 embodying my invention.

The assembly'or structure of a relay 11 is so arranged as to be' mounted on, and secured against, an insulating support 12 which may be either a suitable small panel of electric-insulating material, or it may be a switchboard panel of relatively large area. While 'I have shown such a structure, it is to be noted that my invention is not limited thereto but resides rather in certainfelenients to be hereinafter set forth in greater detail. l

V A magnetizable core-13 its inner end I i engaging-a magnetic'member li, the core memb'e'r'13 being preferably trod'or circular bar shape, while the member 14' may be of substantially plate shape having one surface engaging the surface ofbase 12. Y A non-magnetic yoke portion 16,- o f substantially L- shape, has its shorter leg-portion 17 secured to the front of the plate/14 by any suitable means such as by welding or in any other desired manner. I

A series current-traversed co1l 18 is shown schematically only in the drawing-and while I have shown a coil constituted by a plurality of turns of a relatively heavy current conductor, I may use any other type of energizing coil or any suitable or desired currenttraversed conductor. One terminal of the coil 18 is electrically connected to a bolt or stud 19 by means of which the relay 11 is secured to the base 12. The other terminal of coil 18 is connected to a connector 21 (see Fig. 3), which connector may be of substantially L-shape in section, the connection between the end of coil 18 and member 21 being made by a suitable bolt 22.

A second terminal stud 23 is located on the other side of the coil and core structure, and a second connector 24, also of L-shape, is provided, and a magnetically-reversible strip. or bar 26 extends between the two connectors 21 and 24. This bar may be made of any one of several metals or alloys, and I prefer to use an alloy, usually called invar, which is a 35% or 36% nickel steel. This alloy has the characteristic of being susceptible to magnetism at relatively low temperatures, while it loses its magnetic properties or characteristics at temperatures on the order of 240 C. That is, while an element made of such nickel steel is magnetic at temperatures below approximately 240 C., it becomes non-magnetic at approximately this temperature and then becomes magnetic again upon reduction of temtioned is, therefore, given only for purposes of illustration.

, The bar ,gr strip 26 issecuredtothe two connectors 21 and 24 by any suitable means which may take theform of rivets 27. Further, the area of lateral section of the strip 26 is varied as may be noted by reference to Fig.2 of the drawing, which shows that the lateral width of the strip 26 is less, adjacent to the connector 24, than it is at that end adjacent to connector 21. This 'Wlll havethe result that the temperature value at the reduced section, indicated generally by the numeral 28, will be higher than the tempera- .ture at full section 29, for any predetermined current value traversing the strip 26 after substantially constant temperature values have been established, as will be the case after a certain length of time of operation at such predetermined current value.

An armature structure movable relatively to the non-magnetic support 16 and the core member 13 may comprise a magnetizable member or bar 31 which may be of substantially L-shape in longitudinal section, one leg portion extending parallel to the support 16 and having a projecting knife edge 32 which is located in a shallow recess 33 adjacent to the outer end of the bar 16. A magnetizable tongue member or portion 34 is adjustably and pivotally mounted on the aforesaid leg portion of armature 31 and may be secured in proper or predetermined position relat vely to member 31 by a spring nut 36 engaging a machine screw 37 which machine screw extends through an elongated and laterally extending slot 38 in the tongue member 34 (see Fig. 2). The inner end portion of the tongue member 34 may be offset, as is shown in Fig. 1 of the drawing, and it may have a small rivet 39 projecting beyond that face which is adjacent to the invar strip 26. This is for the purpose of concentrating the magn'etizing flux which traverses the tongue member 34 and the initially magnetic invar strlp 26.

Means for resiliently holding the armature structure, including the portions 31 and 34, in substantially the positions shown in 1g. 1 of the drawing, include a stud 41 which 1s riveted to the non-magnetic member 16 adjacent the forward end thereof, which stud extends through suitable aligned openings in the members 31 and 34, which openings are slightly larger than the stud itself to permit tilting motion of elements 31 and 34 relatively to the stud. A compression spring 42 surrounds the free end of the stud 41 and a washer 43 and a cotter pm 44 permit of giving the spring'42 an initial compression.

The forward end of member 34, which is in general of flat bar shape, may be pointed out as is shown at 46 in Fig. 3, and indicia may be provided on the adjacen surface of member 31, as may be noted by reference to Fig. 3 of the drawing.

The hereinbefore-described construction permits of varying the position of the mem- I ,ber 34, which it may be notedv is also of magnetiz ablematerial such as iron or steel, relatively maybe caused to the member 31, whereby the rivet 39 the upper surface of the invar bar 26at predetermined points along its is possible for the pointer 46 to be set so that it is above the word Low in Fig. 3, and the head of rivet 39 will have been moved toward the left on the invar strip 26 onto a portion of the strip which will be at ahigher temperato normally operatively engage length. Thus, it Y measure ture than other portions of the strip for a predetermined current traversing the coil and the strip 26. If it is desired to vary the adjustment, the spring nut 36 may be loosened and the member'34 turned relatively to the member 31, using the stud 41 as a pivot point and the-pointer 46may thereby be moved over the word High in Fig; 3 of the drawing, when the head of the rivet 39 will operative-1y engage the invar strip 26 at a point where its width is substantially normal.

While I have illustrated and described a structure in which one portion of the armature structure may have a turning or pivotal movement relatively to the other portion of the armature structure, I do not desire to be limited thereto, as lmay move the entire adjustable element laterally of the substantially obvious that, if the movable armature member 34 be so adjusted that the head of the rivet 39 engages the invar strip at its most restricted section 28, the relay will operate at apredetermined value of current traversing the coil, which value is lower than would be required to efiect operation of the relay if the movable armature member 34 were adjusted so that the head of the rivet 39 engaged the magnetically-reversible member at the large section 29.

While I have shown no device which is to be actuated by the moving armature when the depending front leg portion of member 31 is drawntoward the end of core 13, which action occurs when the strip '26 or a predetermined portion thereof has reached the temperature at which that portion loses its-magnetic characteristic, it is obvious that any mechanism may be actuated thereby, such as a push rod, which push rod may, in turn, open a circuit or actuate some other controlling mechanism, as shown, for example, in a patent to H. E. White. No. 1,675,680. July 3, 1928, assigned to the Westinghouse Electric & Manufacturing Company. In view of the well-known application of such elements, I have not thought it necessary or desirable to illustrate such details,=as my invention relates more particularly to means for calibrating or adjusting one part of a thermal relay structure relatively to another part, whereby the 1 Various modifications may be made in my invention without departing from the spirit and scope thereof, and I desire, therefore, that vonly such limitation shall be placed thereon as are imposed by the prior art or are set forth in the appended claims.

I claim as my invention:

1. In a thermal relay including an energizing coil, a magnetic-circuit structure havmg an armature movable relatively to the coil, a heated fixed member having a thermally-variable magnetic characteristic and controlling the position of the armature, said armature having a portion adjustable relatively to the fixed member.

2. In a thermal relay including an energizing coil, a magnetic-circuit structure having an armature movable relatively to the coil, a fixed member heated in accordance with the current traversing the relay and having a thermally-variable magnetic characteristic controlling the position of the armature, said armature having a portion adjustable longitudinally relatively to the heated fixed member.

3. In a thermal relay having an energizing coil and a magnetic circuit structure including a plural part armature movable relatively to the coil, a heated member of varying area of cross-section and having a thermally-variable magnetic characteristic,means for holding said heated member in a fixed position, and means for locking one of said armature parts in predetermined selected position on the other part and longitudinally of the heated member to vary the operation of the relay.

4. In a thermal relay having a currenttraversed member of varying area of crosssection and having a thermally-variable magnetic characteristic, means at its ends for supporting it in a fixed position, a magnetizmg coil structure including a magnetizing coil and a plural-part armature movable relative to the coil, one part thereof being adjustable on the other longitudinally of the current-traversed member.

5. In a thermal relay having a magnetizmg coil, a current-traversed bar of varying area of cross section between its ends, means for holding it in a fixed position relatively to the coil, a support, an armature structure pivotally mounted on the support and including two overlapping portions, and means operatively associated with said armature structure to normally hold the end of one of said overlapping portions in predetermined longitudinally-diiferent positions against the current-traversed bar.

6. In a thermal relay including an energizing coil, a heated member having a thermally-variable magnetic characteristic, a magnetic-circuit structure including an armature embodying two relatively movable portions, means for pivotally mounting said armature, and means on the armature for locking one ofthe ortions on the other to vary the position of the first portion longitudinally of the heated member to vary the operating characteristic of the relay.

7. In a thermal relay including an energizing coil, a heated member having a thermally-variable magnetic characteristic and being of varying area of cross section between its ends, a" current-traversed supporting means in series electric circuit with the energizing coil for holding the heated member in fixed position, a support, an armature pivotally mounted on the support and including two relatively movable portions, and means on the armature for locking one of the portions on the other to vary the position of one of the portions longitudinally of the heated member to vary the operating characteristic of the relay.

8. A thermal relay of the'movable-armature type, comprising magnet-means for magnetizing said. armature and for attracting said armature toward its moved position, and thermally responsive means for holding said armature in its initial position against the pull of said magnet-means, said thermally responsive means comprising a stationary, electric-current-traversed bar of a material which is magnetic when cold and which loses at least some of its magnetism when heated to a critical temperature, said bar being of such spatial disposition that different portions of its length reach said critical temperature at different values and/0r times of flow of the current traversing the same, characterized by means for adjusting the end of the armature which normally contacts with said bar, so that said end 'of the armature may make its contact with the bar at different points along the length of the bar, whereby the current and/or time at which the bar releases the armature is varied.

9. The invention as specified in claim 8, characterized by said bar having a gradually diminishing cross-sectional area from one extreme of the adjustment of said armature to the other.

10. The invention as specified in claim 8 characterized by said armature being a composite member comprising two magnetizable plates pivoted together in face-to-face relation.

11. The invention as specified in claim 8, characterized by said bar having a gradually diminishing cross-sectional area from one extreme of the adjustment of said armature to the other, and further characterized by said armature being a composite member comber, 1931. 1

CHARLES H. HODGKINS. 

